The present invention relates to novel substantially closed-cell fragrant thermoplastic foams and method of making these fragrant thermoplastic foams.
Thermoplastic foams presently have a variety of uses, such as package cushioning, furniture cushioning and thermal insulation.
Generally thermoplastic foams (referred to as "foam" or "foams" in this specification) are produced by feeding a combination composed of a thermoplastic resin and other additives, such as a cell size controlling agent into an extruder, melting the composition under heat to a molten gel, adding a volatile blowing agent to the molten gel, and extruding the resultant molten gel containing the volatile the blowing agent through a die at the end of an extruder into an area having a lower pressure than the pressure inside the extruder.
Thermoplastic foams may be classified as open cell (or pore) and closed cell. The present invention is directed to those thermoplastic foams which are substantially closed cell.
One drawback to some foams is that an odor, which does not quickly dissipate, may be associated with or released by foams and remain detectable for an extended period of time. Some people may find these odors unpleasant. To counteract or overcome this odor released by polyurethane or other synthetic foams having a volatile component which is released over a period of time, artisans added a pleasing scent to the porous foam, including foam rubber. The prolonged release of the fragrance in certain products such as cushions is particularly desirable. Heretofore, however, the scents or fragrances added tend to dissipate quickly and then the original objectionable odor becomes dominant throughout the environment.
It has been known for some time to impregnate articles, having a high degree of porosity, with materials, preferably in the form of liquids, that will evaporate slowly at normal temperatures and pressures and thus permeate the adjacent atmosphere. Further, various sustained release means comprising a polymeric carrier have been proposed, i.e., U.S. Pat. Nos. 3,857,932; 3,975,350 and 4,202,880. Among the materials that may be impregnated into porous materials have been medications, perfumes, deodorants, germicides, pesticides, disinfecting and sterilizing agents, etc.
It is also known to the compounding art that agents not soluble within a thermoplastic polymeric matrix will not move at an efficacious rate through the matrix to the matrix surface and then enter the ambient environment. Solubility is not generally a problem wit an open cell foam. However a substantially closed cell foam behaves much like a nonfoamed thermoplastic resin in that the incorporated fragrance must move at an efficacious rate through the closed cell foam matrix to the foam surface and then enter the ambient environment. With substantially closed cell foams each cell wall is a new barrier to be crossed for the incorporated fragrance. Thus the incorporation of the fragrance into a substantially closed cell foams greatly increases the overall time for the release of the fragrance to the ambient atmosphere.
U.S. Pat. No. 4,339,550 discloses hydrophillic polyurethane foam products characterized by a cross-linked, non-linear molecular network which incorporate active materials, utilizing in situ methods, into the cell structure of the hydrophillic polyurethane foam so that the active material has a controlled release.
U.S. Pat. No. 4,254,179 describes how to overcome new carpet and foam underlay odor by impregnating the padding with a lasting fragrance, either in the form of an encapsulated fragrance which is slowly released as the foam is later used or a slow release fragrance which is long lasting due to the manner in which it is incorporated in the foam. The foam underlay in the form of a planar sheet is impregnated with a fragrance by application of particles carrying a fragrance to one major surface of the foam sheet. Heat may be applied to the underlay to cause the particles to migrate into the body of the foam. A vacuum is applied to the opposite surface of the foam causing the particles to migrate further into the foam. In addition, mechanical spreading of the particles as by brushing or wiping may be used to distribute the particles across the foam surface and into open voids in that surface. Finally, a semi-pervious layer may be bonded to the foam surface over the particles to retain them in place. In this manner a long lasting fragrant porous foam product is obtained.
These teachings however do not teach a fragrant substantially closed cell thermoplastic foam or a method for making this foam.